Low smoking nickel aluminum flame spray powder



. idea- 570. oa 3.338.688 an 3,338,688 Patented Aug. 29, 1967 i United States Patent "ice example, should have a size between --60 mesh and +3 microns, and preferably 140 mesh and +10 microns, the mesh sizes being US. Standard Screen Mesh sizes. Most preferably the powder should be as uniform as pos- 5 sible in grain size, with the individual grains not vary- SPRAY POWDER Frank N. Longo, Mineola, N.Y., assignor to Metco Inc., Westbury, N.Y., a corporation of New Jersey No Drawing. Filed Oct. 6, 1964, Ser. No. 401,969 8 Claims. (Cl. 29192) This invention relates to a low smoking nickel aluminum nickel particles should have the general over-all shape and size of conventional flame spray powders and thus, for

ing by more than 240 microns and preferably 75 microns.

The initial nickel particles which constitute the core or nucleus of the composite powders in accordance with the invention should have a size and shape approximating that desired in the end powders as described above.

flame spray powder. The invention more particularly re- 10 lates to a nickel aluminum composite flame spray powder The nickel core or nucleus particles are then coated with which may be flame-sprayed to form a self-bonding coatthe aluminum and nickel boron, the coating being effected ing With the generation of considerably less smoke than by any known coating process, as for example described the previously known self-bonding nickel aluminum flame in copending application Ser. No. 343,705, filed Feb. 10, spray powders or other self-bonding flame spray ma- 1964. terials. Preferably the aluminum and the nickel boron are de- In flame spraying the surface or base, such as the posited in finely divided form in a binder on the nickel metal surface or base being coated by the flame spray particles. technique, must generally have a special surface prepa- The aluminum and nickel boron, preferably in as finely ration such as a severe mechanical roughening in order divided form as possible, as for example a size of -325 to ensure a satisfactory bond of the sprayed coating. mesh, are mixed in the required proportions with a Certain materials, as for example molybdenum, will howbinder or lacquer so as, in elfect, to form a paint in 7 ever adequately bond to a clean surface without this spewhich the aluminum and nickel boron particles correcial surface preparation and of course subsequently apspond to the pigment. The paint is then used to coat the plied sprayed layers will adequately bond to the initially i kel o e rti le and allow d to set or dry. applied sprayed coating as one flame-sprayed layer bonds The binder material may be any known or conventional to a previously applied layer without difficulty. Materials, binder material which may be used for forming a coating such as molybdenum, which will bond to a base Without or for bonding particles together or to a surface. The the conventional surface preparation, are referred to in binder is preferably a varnish containing a resin as the the flame spray art as self-bonding. A further self-bondvarnish solids, and may contain a resin which does not ihg flame spray material is a Composite Composed of depend on solvent evaporation in order to form a dried nickel and aluminum which will exothermically react r set film, The varnish may thus contain a catalyzed when p y forming a nickel ahlmihide intefresin as the varnish solids. Examples of binders which metallic. may be used include the conventional phenolic, epoxy, The known Self-bonding flame p y materials generate or alkyd varnishes, varnishes containing drying oils, such a C nsid rable am llnt f Smoke d g praying and this as tuna oil and linseed oil, rubber and latex binders and presents a problem if adequate ventilating facilities are th 1ik not Provided, as for example Where Special exhausting The coating of the nickel core component with the facilities, such as an exhaust booth, are not available. pain containing the aluminum and nickel boron may It has been found that the amount of smoke generated b ff t d i any know or desired manner, and it is y the nickel aluminum composites y be reduced y simply necessary to mix the two materials together and reducing the percentage of the aluminum in the cOmallow the binder to set or dry, which will result in a P but this results in a corresponding reduction 0f fairly free-flowing powder consisting of the nickel core the bond Strength of the Coating formed, and it has 110t coated with cladding of the aluminum and nickel boron. been possible to reduce the smoke to a tolerable level 4 Th i k 1 bo der may be any known powder while retaining a satisfactory bond strength. comprising afi ialjjyjlgflnjekel and boron containing for One object of this invention is a Self-bonding fl example, from 5 95% boron, andpr'efer'ably from 7 25% spray powder which will generate substantially less smoke by i ht of boron, and most preferably about 18% by When p y than the Prior art Powders and Still retaln Weight boron. The nickel boron powder most preferably ahigh bond strength. is used in a particle size range between -20 and +1 A further object of this invention is an aluminum coated i nickel flame P Y Powder which is Self-bonding When The powders are sprayed in the COHVCIllIlOI'IEII manner, sprayed and which will generate substantially less smoke using a powder type flame spray gun, though it is also than the conventional nickel aluminum composite powders ibl t bi h Same i th f f a wlre While retaining a high bond Strength rod, using plastic or a similar binding, as for example These and Still furth r Objects Will become apparent polyethylene which decomposes in a heating zone of the fro the following desel'iptiohi gun. When formed as wires, the same may have conven- In accordance with the invention I have discovfired that tional sizes and accuracy tolerances for flame spray wires a particular form of a nickel aluminum composite flame and thus for example, may Vary in Size between and spray powder containing a specific additive will produce 20 gauge. substantially less smoke when sprayed than the other The spraying is in all respects efiected in the convem known nickel alllminum composlte flame spray-powder; tional manner previously utilized for self-bonding flame laandcyvill retain hlgh bond strength or even show lncrease p y material, and in particular nickel aluminum n stren The com posite flame spray powder in accordance with posfltes Due jfi ifigg a gc ad zl dz riiii il ii i the invention comprises nickel particles coated with $111 e Prepara 1 f g 1 to 6% by weight f aluminum and 1 to 2% by required thou h, of course conventiona sur ace prepara- Weight nickel boron, based on the total of aluminum, e ut'lhzed 1f deslmd- The Powder m accfrdance nickel boron and nickel in the particles with the invention may be flame-sprayed as a bonding coat The composite of aluminum and nickel boron coated for q n ly ppli d flame spray material or any purposes where it is desiredto form the nickel aluminide coating. The composites may furthermore be sprayed in conjunction with, or in addition to, other flame spray materials conventionally used in the art.

When sprayed, the nickel and aluminum exothermically react, forming a nickel aluminide intermetallic.

The following examples are given by way of illustration and not limitation:

EXAMPLE 1 Finely divided aluminum powder (325 mesh) was admixed with 20% by weight of nickel boron powder based on aluminum, consisting of a foundry alloy containing 18% by weight of boron and having a particle size between about l-20 microns. The powder blend was then admixed with a conventional phenolic varnish having approximately 10% solid contents so as to form a mixture having the consistency of heavy syrup and containing about 60% by weight of the metal particles. 100 grams of the varnish powder mixture is then added to about 900 grams of nickel powder having a size between about 200- 325 mesh and the two are thoroughly mixed, with the mixing continued until the varnish dries leaving a fairly free-flowing powder in which all of the nickel core particles are clad with a dry film which contains the aluminum particles and nickel boron particles. The powder is then warmed to about 250 F. to ensure complete drying. The powder is then screened and hand-milled to reduce the same to a 100 mesh powder. The end powder consists approximately of 5% aluminum, 1% nickel boron, the balance nickel. The powder is flame-sprayed on a mild am plate which has been surface cleaned by smooth grinding. The spraying is effected at a distance of 6 from the plate, using a powder type flame spray gun as described in US. Patent 2,961,335 of Nov. 22, 1960 and sold by Metco, Inc., of Westbury, N.Y., under the trade name Thermospray powder gun. The spraying is effected at a rate of 5 to 10 lbs. of powder per hour, using acetylene gas as the fuel, at a pressure of 10 lbs. p.s.i. gauge and a flow rate of cu. ft./hr., and oxygen as the oxidizing gas at a pressure of 12 lbs. p.s.i. gauge and a flow rate of cu. ft./hr. During the spraying very little smoke is generated and a coating layer is built up to a thickness of between .003" and .005. The coating is self-bonded, has excellent oxidation resistant characteristics even at high temperatures, and can be used as an intermediate bonding coat.

EXAMPLE 2 Example 1 was repeated except that three batches of powder were made up containing 3, 4 and 5% by weight of aluminum, respectively, each containing 1% by weight of nickel boron. Each of the powder batches was sprayed as described in Example 1 and the amount of smoke generated was determined on the basis of the amount of time it took for the smoke to fill a booth having a volume of 36 cu. ft. The bond strength of the coatings produced for each of the batches was also tested in the conventional manner by spraying on the end face of a mild steel rod of approximately 1" diameter, grinding the sprayed coating smooth, and cementing a second, similar rod to the ground steel and pulling the two rods apart in tension and determining the force necessary to lift the coating.

Table I below indicates the results:

4 EXAMPLE 3 Example 2 was repeated exactly except that in each case the flame spray powder was formed without the nickel boron. The results obtained are shown in Table II below:

TABLE II Aluminum Bond Smoke, time to fill Content Strength" 36 cu. ft. volume (percent) (p.s.i.) (see) These figures are averages of 6 or more tests.

EXAMPLE 4 Example 1 may be repeated, using in place of the nickel boron foundry alloy, nickel boron alloys containing from 5-95 and preferably 7-25 boron.

While the invention has been described in detail with reference to certain specific embodiments, various changes and modifications which fall within the spirit of the invention and scope of the appended claims, will become apparent to the skilled artisan. The invention is, therefore, only intended to be limited by the appended claims or their equivalents wherein I have endeavored to claim all inherent novelty.

I claim:

JEIQL BEY. w la comprising parades h a nickeLcore cpated with aluminum and nickel boron.

2. A flame spray powder comprising particles having a nickel core coated with about 2 /2 to 6% by weight of aluminum and /2 to 2% nickel boron based on the total of nickel, aluminum and nickel boron.

3. A flame spray powder according to claim 2 in which said nickel boron is present in amount of about 1% by weight.

4. we spray powder comprising pa rti c les h aying a n igkel gore coated with {binder containing aluminum particles and nickel borompart icles, said aluminum par ticles being present in amount of 2 /2 to 6% by Weight based on the total of aluminum, nickel and nickel boron, said nickel boron particles being present in amount of about /2 to 2% by weight based on the total of the aluminum, nickel and nickel boron.

5. A flame sppaypowder according to claim 4 in which said inder is ayarniish:

6. A flame spray powder according to claim 5 in which said niekel b o'foni present in amount of about 1% by weight.

7. A flame spray powder according to claim 6 in which said aluminum is present in amount of about 5% by weight.

8. In the flame spray process, the improvement which comprises spraying a flame spray powder comprising particles having g pickel core cop tec l a minor amount of aluminum and nickel boron. w

References Cited UNITED STATES PATENTS 3,025,182 3/1962 Schrewelius l17105 3,141,744 7/1964- Couch et al 29194 3,254,970 6/1966 DittIiCh et a1. 2919l.2 3,305,326 2/1967 Longo 29-192 DAVID L. RECK, Primary Examiner.

R. O. DEAN, Assistant Examiner. 

1. A FLAME SPRAY POWDER COMPRISING PARTICLES HAVING A NICKEL CORE COATED WITH ALUMINUM AND NICKEL BORON. 